Due to the their widespread use and stability, sediments contaminated with persistent organic pollutants (POPs) such as polychlorinated biphenyls, chlorobenzenes and dioxins have been an environmental concern for several decades. In addition to perturbing the benthic community, these compounds biomagnify in the food chain through accumulation in the fatty tissue of animals, such as fish and marine mammals, which can eventually affect humans if consumed. Exposure to halogenated POPs by humans can lead to dermal toxicity, teratotoxicity, endocrine effects, hepatotoxicity, immunotoxicity, and carcinogenesis. Although chemically stable in the environment these highly chlorinated compounds are susceptible to degradation once most of their chlorines are removed. The initial dechlorination is catalyzed in the anaerobic environment by microbial reductive respiration;the products of this initial microbial process can then be degraded and detoxified by oxygen respiring microorganisms. The limitations of these processes are: 1) anaerobic dechlorination is often slow and incomplete;2) aerobic degradation is inhibited by limited availability of oxygen in the anaerobic sediment regions where these compounds persist. The Principal Investigators propose to complete the anaerobic process to unflanked di- through tetrachlorinated by in situ bioaugmention with dechlorinating microorganisms followed by application of low current hydrolysis to provide a constant level of oxygen for the complete degradation of the chlorinated compounds. The innovative aspects of this approach include the use of dechlorinating species with specific activities to direct the anaerobic dechorination pathways, a unique process for scaling up dehalogenating inoculum without co-release of toxic chlorinated compounds, electrolysis of water for maintaining constant oxygen levels during aerobic degradation and high throughput molecular assays for monitoring microbial communities. This integrated approach will optimize both anaerobic and aerobic processes to achieve complete in situ detoxification of chlorinated compounds through mineralization to small molecular weight metabolites and carbon dioxide. Implementation of a tractable in situ detoxification process to organohalide impacted sites will mitigate exposure to the food chain and subsequent exposure risks to the general public.